Foamed ceramic



CROSS REFERENIIE EXAhiiiiI-IR United States Patent 3,330,675 PatentedJuly 11, 1967 "ice Al O :P O appreciably greater than 1 to 2, it hasbeen 3,330,675 found that the viscosity of the acid aluminum phosphateFOAMED CERAMIC Jules Magder, Cleveland, Ohio, assignor to Horizons e Nol fifi v gf l il ed I ehl 5 f l324? S l l 32 2,771 5 In practice, it hasbeen found that once the ratio of 5 Cl i ((31, 106-40) Al O :P O hasbeen selected, the preferred range for the ratio of P O :H O for theacid aluminum phosphate solu- This invention relates to a light weightinsulating cetion may be deduced experimentally, by ascertaining theramic material and to the manner in which it is formed. quantity ofwater necessary to give a viscosity for the More particularly it relatesto improvements over the cesolution in the range of 800 to 6000centipoises at 72 ramic compositions described in copending UnitedStates F., as measured, for example, with a Brookfield Viscosimpatentapplication Ser. No. 161,426, filed Dec. 22, 1961, eter using a number 4spindle at 60 rpm. now abandoned Like the compositions described in theabove noted THE BASIC COMPOUND patent application, the ceramiccompositions of this in- Y haste Compound is meant a compound of anvention are capable of being foamed and formed into element selectedfrom the g p consisting of magnesium, useful porous cellular productswithout the application Zirconium, strontium, barium, aluminum, lithium,and f h t f anyeXtema1SOui-ce iron, selected from the group consistingof oxides, hy-

A specific bj t of this invention is to modify the droxides, silicates,and carbonates, or mixtures or solid positions described in the abovenoted patent application solutions of such compounds It is evident thata number i order t bt i d q hi h h i d h i l of minerals fall into thisclassification, such as wollastoproperties as compared with the productsobtainable from hite, tale, asbestos, Zircon, Olivine, In the Practicethe compositions described in the aforesaid patent applicaof the Presentinvention haste compounds of magnesium ti and zirconium representpreferred species because when The compositions described and claimed insaid patent used in the composition, the resulting teams haveapplication comprise the following essential constituents: haheed P yProperties as compared with the teams A liquid hi l water b i f d;resulting from the use of wollastonite as the basic com- (b) An acidicphosphate selected from the group con- P sisting of acidic aluminumphosphate, acidic calcium phosy suitable reactivity of the basicCompound; is meaht phate and acidic zirconium phosphate, the acidicalumithat when equivalent amounts of the basic mpound and num phosphatebeing preferred; the acid aluminum phosphate solution are mixed at tem-(c) Afincly divided calcium silicat gand peratures above 60 F. but below220 F., the mixture 1) A ll amount f a gas lib ti h i 1 sets to a solid,monolithic, tack-free mass within periods Briefly i h resent i ti otherb i less than about /2 hour, but greater than about 1 minute. pounds ofsuitable reactivity, as hereinafter defined, are The approximate minimumratio of the q y of substituted for the calcium silicate in the foamcomposihaste compound mixture of basic compounds, to tions with theresult that a substantial increase in coldthat of the acid aluminumPhosphate solution y be setting bond strength, softening temperature,and resistcalculated according to the following formula: ance tocracking at elevated temperatures are obtained.

More specifically, in accordance with the present in- 40 Eb equals EH05mmu s EA12O3 vention, a solution of acid aluminum phosphate of suit-Where Eb 15 total number 9 equlvalents of basic able composition ismixed with a basic compound of Pound mtxtures of baslc compounflsi andPz a suitable reactivity as defined below, of an element selected and zs are eztch the h of equlvalehts of 2 5 from the group consisting ofmagnesium, z rconi and Al- Q respectively, contained in the requiredquantity strontium, barium, aluminum, lithium, and iron, or mixof theacld alummum Phosphatesolutlom tures of these compounds, in the presenceof a substance For Purposes of thls calcutatlohi the number of q whichliberates a gas during or after the mixing process, alent? of a compound'e of compounds, is and of which the liberation of the gas issubstantially termlned e the 3 of the equlvalents contributed ycompleted prior to the setting or hardening of th the constituent oxidespresent; the equivalent weight of m i a solid mass a constituent oxideis in turn determined by multiplying THE ACID PHOSPHATE its formulaweight by the factor given in the table below.

The preferred acid phosphate in practicing this inven- 0 to deterfmnetion is an acid aluminum phosphate although both the eqmvalent welghltcalcium and zirconium phosphates described in US. Ser. A; No. 161,426may also be used in place of the acid alumi- C num phosphate. 3

A suitable composition for the acid aluminum phos- M 8 A phate solutionis one in which the ratio of Al O :P O is 1 greater than 1 to 5 but lessthan 1 to 2, expressed as moles, and in which the ratio of H O:P O isgreater than 0 approximately 5 to 1, but less than approximately 15 to1, also expressed as moles. In thus specifying the suitable /2 range ofcomposition of the acid aluminum phosphate 1 solution, the totalcomposition of the solution has been 3 As expressed in terms of theratios of the three oxides A1 0 P 0 and H 0. It has been found that whenan acid It Will be noted that the oxides, hydroxides, silicates aluminumphosphate solution with a ratio of Al O :P O and carbonates comprisingsaid basic compound, the appreciably less than 1 to 5 is employed, theheat of the oxides SiO H 0 and CO are considered to contribute reactionwith the basic compound is so great that volatil- 7O nothing to thenumber of equivalents present.

ization of water, and consequent collapse of the foam, occur on mixing.On the other hand, with ratios of solution is so great that sufficientlythorough mixing is impossible.

In practice, when calculating the minimum quantity of basic compound, itis to be understood that the foaming agent is to be considered as abasic compound if such foaming agent partially neutralizes theequivalent excess of P in the acid aluminum phosphate solution. In thecase of a metallic foaming agent such as aluminum or zinc, theequivalent weight of such metal is calculated as that weight whichyields an equivalent of the oxide of the metal, as defined above.

It is thus readily seen that for a given quantity of acid aluminumphosphate solution the minumum total quantity of basic compounds informulations which constitute the present invention is that quantitywhich corresponds to complete neutralization of the excess P 0 presentin the acid aluminum phosphate solution. In practice, optimum quantitiesof basic compounds are found to be slightly greater than the minimumquantity, but do not exceed the quantities which give a readily mixablepaste when initially combined with the acid aluminum phosphate solutionin the presence of the foaming agent.

THE GAS FCRMING AGENT Suitable gas-forming agents include (a)carbonates, in particular the carbonates of calcium, magnesium,strontium, barium, lithium, ammonium, and iron; (b) metals such asaluminum, magnesium, zinc and iron each of which reacts with phosphoricacid with the liberation of hydrogen; (c) compressed or liquefied gasesor volatile liquids, such as compressed air, nitrogen, carbon dioxide,trichloromonofiuoromethane, dichlorodifiuoromethane; (d) hydrogenperoxide, ammonium nitrite andN,N'-dimethyl-N,N-dinitrosoterephthalamide, or other similar gasforming, readily decomposable compounds.

The metal compounds or ammonium compounds are basic compounds since theycan react with or form products which react with the phosphoric acid.The other gas forming compounds are neutral in the sense that they donot engender partial neutralization of the excess P 0 present in theacid aluminum phosphate solution.

To ascertain the quantity of foaming agent for a given total weight offormulation, a knowledge of the gas-forming reaction facilitatescalculation of the total theoretical quantity of gas produced, andhence, the resulting contribution of the liberated gas to the specificvolume of the foam.

For the indicated carbonates as foaming agents, the gas-forming reactionis:

M CO +2H+ CO +2M++H 0 wherein M is an equivalent of the metal of whichthe composable compounds, the gas-forming reactions are, respectively,

In practice, a sufficient quantity of gas-forming agent is used toprovide a specific volume of the foam in the range of approximatelybetween 10 and 1 cubic centimeters per gram, that is to say, a densityin the range of approximately 6.2 to 62 pounds per cubic foot in thefoamed product.

The following examples are intended to illustrate, but not to restrict,embodiments of the present invention.

Example 1 Part A: Parts by weight Acid aluminum phosphate solution withratio Al O :P- ,O :H O=0.823:26.0 39 Part B:

Wollastonite, minus 325 mesh 53 Aluminum hydroxide, light grade 6Aluminum metal 2 To prepare the foam, part B is pre-blended and thenmixed with part A for a period of not more than two minutes. Thiscomposition foams and sets in about 10 minutes to a density of 35 poundsper cubic foot. The compressive strength is about 450 pounds per squareinch.

Examples 2 and 3 Example 2- Parts by Weight Example 3- Parts by WeightPart A":

Acid aiurnlnum phosphate solution,

With AlzOzZPzOsIHzO=0.8Z3118.5... 55 55 50% aqueous benzyi trimethylarumonium chloride solution Part B":

Tale, minus 200 mesh 42 44 Aluminum powder, pigment grade 3 1 Parts Aand B are pre-blended separately and then mixed for a period preferablynot greater than about 3 minutes. The mixture is transferred to asuitable mold, where foaming begins in about five minutes after mixingis completed; the mixture then becomes hot and sets to a rigid cellularmass. Example 2 yields a foam density of about 30 pounds per cubic foot,and Example 3, 42 pounds per cubic foot.

A freshly prepared specimen of Example 2 may be shock-heated to 2400" F.Without any significant change in strength or in linear dimensions, asillustrated in Table 2.

TABLE 2.-EFFECTS OF SHOCK-HEATING A 3-INCH CUBE SPECIMEN OF FOAM,PREPARED ACCORDING TO EXAMPLE 2 FOR 15 LIINUTES AT 2400 F To prepare thefoam, parts A and B are preblended separately, the latter preferably bymeans of a twin-shell type of dry blender; the parts are then mixed, andallowed to foam and set for about 24 hours at about F. The density ofthe product is about 26 pounds per cubic foot,

and the compressive strength about 800 pounds per square inch.

Example 5 Part A: Parts by weight Acid aluminum phosphate solution, withratio A1203:P205:H20=0.9:3.0Z23.5 Silicone fluid, Dow Corning DC-l130.05 Part B:

Zircon, minus 200 mesh 68.5 Aluminum hydroxide, light grade 5 Aluminummetal 1.5

To prepare the foam, parts A and B are pro-blended separately and thenmixed together for a period preferably not more than 4 minutes. Thecomposition begins to foam about 5 minutes after the mixing iscompleted, and sets in about minutes to a density of 55 pounds per cubicfoot. The compressive strength of the foam is about 650 pounds persquare inch, and the softening temperature is about 3300 F.

An apparatus particularly suitable for producing the foamed ceramics ofthis invention is described in an application 'Ser. No. 342,730 filed ofeven date herewith and now abandoned.

I claim:

1. A composition which when the several ingredients are brought togetheris capable of setting into a porous monolithic ceramic mass without theapplication thereto of any heat from an external source, saidcomposition consisting essentially of:

a first constituent consisting of an aqueous solution of an acidicaluminum phosphate in which the relative molar proportions of Al O :P Ois greater than 1:5

and less than 1:2 and in which the relative molar proportions of H O:P Ois greater than 5:1 and less than 15:1; and a second constituentconsisting of at least one basic compound selected from the groupconsisting of the carbonates, oxides, hydroxides and silicates of ametal selected from the group consisting of magnesium and zirconium; anda gas producing material selected from the group consisting of thecarbonates of Ca, Mg, Sr, Ba, Li, vNH and Fe; the metals Al, Mg, Zn andFe; compressed gases and liquids; and readily decomposable compoundswhich form gases at room temperature when brought into contact with theremaining constituents of the composition; the relative number ofequivalents of basic compound in said composition being equal to thenumber of equivalents of free P 0 in said acidic aluminum phosphate. 2.The composition of claim 1 wherein the compound of magnesium is talc.

3. The composition of claim 1 wherein the compound of zirconium iszircon.

4. The composition of claim 1 wherein the gas producing material is ametal.

5. The composition of claim 4 in which the metal is aluminum.

References Cited UNITED STATES PATENTS HELEN M. MCCARTHY, PrimaryExaminer.-

1. A COMPOSITION WHICH WHEN THE SEVERAL INGREDIENTS ARE BROUGHT TOGETHERIS CAPABLE OF SETTING INTO A POROUS MONOLITHIC CERAMIC MASS WITHOUT THEAPPLICATION THERETO OF ANY HEAT FROM AN EXTERNAL SOURCE, SAIDCOMPOSITION CONSISTING ESSENTIALLY OF: A FIRST CONSTITUTENT CONSISTINGOF AN AQUEOUS SOLUTION OF AN ACIDIC ALUMINUM PHOSPHATE IN WHICH THERELATIVE MOLAR PROPORTIONS OF AL2O3:P2O5 IS GREATER THAN 1:5 AND LESSTHAN 1:2 AND IN WHICH THE RELATIVE MOLAR PROPORTIONS OF H2O:P2O5 ISGREATER THAN 5:1 AND LESS THAN 15:1; AND A SECOND CONSTITUENT CONSISTINGOF AT LEAST ONE BASIC COMPOUND SELECTED FROM THE GROUP CONSISTING OF THECARBONATES, OXIDES, HYDROXIDES AND SILICATES OF A METAL SELECTED FROMTHE GROUP CONSISTING OF MAGNESIUM AND ZICRONIUM; AND A GAS PRODUCINGMATERIAL SELECTED FROM THE GROUP CONSISTING OF THE CARBONATES OF CA, MG,SR, BA, LI, NH4 AND FE; THE METALS AL, MG, ZN AND FE; COMPRESSED GASESAND LIQUIDS; AND READILY DECOMPOSABLE COMPOUNDS WHICH FROM GASES AT ROOMTEMPERATURE WHEN BROUGHT INTO CONTACT WITH THE REMAINING CONSTITUENTS OFTHE COMPOSITION; THE RELATIVE NUMBER OF EQUIVALENTS OF BASIC COMPOUND INSAID COMPOSITION BEING EQUAL TO THE NUMBER OF EQUIVALENTS OF FREE P2O5IN SAID ACIDIC ALUMINUM PHOSPHATE.